This invention relates to a power control unit for a system comprised of a MAIN computer and peripheral devices such as a floppy disk device and more particularly to such a power control unit for a portable system using a battery as its power source.
Consider, for example, a computer such as a pocketsize computer which can be operated from a DC source. Since such a computer uses CMOS, the range of its operating voltage is quite large. If the range of the operating voltage of a peripheral device such as a printer connected to such a computer is narrower than that of the main computer itself, it is not possible to operate such a peripheral device stably because the source voltage from the main computer is too low. One way to overcome this problem is to provide such peripheral devices with their own source voltage generating circuits for generating the source voltages required thereby such that power is supplied to a main computer and its peripheral devices from separate source circuits. Since a main computer is more frequently used alone rather than in combination with a peripheral device, however, it often happens that the power source for the main computer is consumed quickly. In the case of a battery-operated computer, in particular, the user finds it inconvenient to exchange batteries frequently.